Mix together spinach-cheese mixture until smooth, melt for 20 secs in the microwave if needed to easily stir.
In a separate bowl, mix parmesan butter then spread on the outside of the slices.
Assemble sandwich by adding spinach mixture, salmon, and slices of cheese.
Add a little butter to the skillet then place over low heat in a non-skillet and toast on each side until browned.
